1. Field of the Invention
The invention relates to an agent and a device for preventing deterioration of an engine oil. In particular, the invention relates to an agent and a device for preventing deterioration of an engine oil by adding the agent to the engine oil when an amount of the agent already included in the engine oil is decreased.
2. Description of the Related Art
An engine oil functions to lubricate movable parts of an engine to decrease the friction therebetween and prevent the wear thereof. The engine oil is exposed to a severe environment. Further, the engine oil is deteriorated due to material coming from a combustion chamber of the engine. The material includes acid material such as a sulfuric acid or a hydrochloric acid generated from a combustion gas, unburned fuel, a sludge component and carbon. In order to prevent the deterioration of the engine oil, some agents for preventing the deterioration of the engine oil (hereinafter referred to as "addition agent") are mixed in the base oil.
The basic addition agent normally used includes a metal cleaner, an oxidation inhibitor, an ash-free dispersing agent, a wear preventing agent, an ash-free rust preventing agent, a viscosity index improver, a pour point depressant, an antifoaming agent, a corrosion preventing agent, and a friction adjusting agent.
The engine oil is deteriorated due to the deterioration of the engine oil itself. The deterioration of the engine oil itself is due to oxidation of the base oil and the addition agents, generation of an organic oxide by a heat decomposition, and consumption of the addition agents.
Further, the engine oil is deteriorated due to dirt in the engine oil. The dirt in the engine oil is due to a mixture of metal abrasion powders, combustion products or dust included in the air into the engine oil.
In order to prevent the dirt remaining in the engine oil, as disclosed in Japanese Unexamined Patent Publication 3-290012, an oil filter comprising a filter element in the form of a paper is provided in a lubrication system to filter the engine oil to eliminate foreign matter from the engine oil. The filtering efficiency is increased and the lifetime of the above oil filter is extended.
Using the above oil filter, the dirt in the engine oil can be removed. However, the above oil filter cannot prevent the deterioration of the engine oil itself due to a decrease in the amount of the addition agents included in the engine oil. Further, the above oil filter may trap the addition agents included in the engine oil. As a result, the amount of the addition agents which can flow in the lubrication system is decreased.
Therefore, the object of the invention is to add addition agents to the engine oil according to the decrease in the addition agents already included in the engine oil to prevent the deterioration of the engine oil.